This proposal describes a training program to advance my academic career in biomarker development for oncology. The purpose of this award is to encourage my independent research program, and this period will be used to expand my scientific knowledge and mentoring skills. During the K99 award period, I will be mentored by Dr. Charles Sawyers and co-mentored by Dr. Jason Lewis. Dr. Sawyers is an internationally recognized expert in clinical oncology, in particular, the development and assessment of targeted molecular therapeutics for hematological and prostate cancers, and has a longstanding interest in technologies that define drug pharmacology in vivo. Dr. Lewis is an Inorganic Chemist and Radiochemist with substantial experience in the preclinical validation and clinical translation of novel radiopharmaceuticals for imaging and therapy. Drs. Sawyers and Lewis have mentored many scientists and clinical fellows, several of whom have transitioned to successful academic careers. Memorial Sloan Kettering Cancer Center (MSKCC) will provide institutional support to me, including the resources to conduct laboratory research, opportunities to foster career development and continuing education, and an open scientific environment to foster the interaction required for me to achieve my goals.The overall goal of this research proposal is for me to learn the theory and practice of Radiochemistry in the context of developing new applications for zirconium-89 labeled transferrin (89Zr-Tf), a novel radiotracer for PET I co-invented at MSKCC. The proposal extends directly from my previous experience, as 89Zr-Tf is one of three novel radiotracers for Positron Emission Tomography (PET) that I developed through collaborations to measure androgen receptor (AR) or MYC signaling in prostate cancer. This research has established that genetic or pharmacologically driven changes in oncogenic signaling pathways can be non-invasively measured with PET imaging, further underscoring a role for molecular imaging in oncology. The specific aim of this proposal during the 2-year K99 award period is to use 89Zr-Tf to study the role of MYC in tumor response to targeted therapies (Specific Aim 1). The specific aims for the 3-year R00 award period extend from this aim, and are (1) to demonstrate that 89Zr-Tf can measure pharmacologically triggered changes in PI3K pathway signaling in prostate cancer models (Specific Aim 2, and (2) to determine whether 89Zr-Tf uptake is reflective of aberrant PI3K pathway signaling in preclinical models of glioblastoma multiforme (Specific Aim 3), two pathologies for which novel imaging biomarkers are urgently needed.